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Rendering gems with aterism or chatoyancy

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In this paper we describe an algorithm to render the asterism or chatoyancy effect in gems. This effect is due to light dispersion caused by inclusions consisting of vast numbers of thin fibrous needles. We develop models for distribution of the microfacet directions of the inclusions and of the light dispersion by them. Based on these models we derive an algorithm to render gems with the asterism effect. By introducting a ray distribution map, a new algorithm for tracing dispersed light rays is developed.

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  1. Whitted T (1980) An improved illumination model for shaded display, Commun ACM 23:(6) 343–349

    Article  Google Scholar 

  2. GIA, Gemological Institute of America (1977) Colored stones, Assignment No. 9

  3. Wuthrich, A., Weibel M (1981) Optical theory of asterism. Phys Chem Minerals 7:53–54

    Article  Google Scholar 

  4. Blinn JF (1977) Models of light reflection for computer synthesized pictures. Proc Siggraph 77, pp 192–198

    Google Scholar 

  5. Hall RA, Greenberg DP (1983) A testbed for realistic image synthesis. IEEE Comput Graph Appl 3(8): 10–20

    Google Scholar 

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Yokoi, S., Kurashige, K. & Toriwaki, Ji. Rendering gems with aterism or chatoyancy. The Visual Computer 2, 307–312 (1986).

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